Prevalence of HRR gene mutations in patients with metastatic castration-resistant prostate cancer: Germline results from the Latin-American observational study PROSPECT

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Background: Metastatic castration-resistant prostate cancer (mCRPC) is a molecularly heterogeneous disease, and 20% to 30% of patients harbor alterations in homologous recombination repair (HRR) genes. However, data regarding the genetic profile of mCRPC in Latin American populations are scarce. This study determined the prevalence of HRR gene mutations in Latin American patients with mCRPC to better understand this population and guide future policies. The interim analysis herein reports results focused on germline alterations only. Methods: PROSPECT (NCT04962880) is a cross-sectional, non-interventional, multicenter study. Patients were adults (≥18 years) diagnosed with mCRPC from November 2020 to October 2021 at centers in Argentina, Brazil, Colombia, Costa Rica, Mexico, Panama, and Peru. Diagnoses were confirmed by laboratory testing (PSA and/or testosterone levels) or imaging (X-ray, CT, MRI, or PET scan). All patients provided written informed consent. Blood samples were assayed to determine the prevalence of germline mutations in HRR genes in the participating countries using the AmoyDx HANDLE HRR Next Generation Sequence 32 genes Panel (AmoyDx, Xiamen, China). Results: Overall, 388 participants with a median age of 70 years (range: 49‒89) were included in this study, including 184 Hispanic (47.4%), 101 White (26%), 40 Mestizo (10.3%), 11 African American (2.8%), 2 Asian (0.5%), and 50 “other” (12.9%) patients. Over a third of them (n=151, 38.9%) had a family history of cancer. Median time since prostate cancer diagnosis was 3 years (range: 0‒23) and 2 years (range: 0‒22) since mCRPC diagnosis. Metastases were most frequently localized to the bones (59.6%). The patients’ ECOG status was either 0 (173/365; 47.4%) or 1 (192/365; 52.6%). Among the 167 patients that received treatment, most received androgen deprivation therapy alone (43.7%) or with radiotherapy (21.6%). Overall, 25/381 patients (6.56%) had germline HRR mutations. The 5 most frequently mutated HRR genes were BRCA2 (16%), ATM (12%), CHEK2 (12%), BRIP1 (8%) and HOXB13 (8%). Conclusions: The prevalence of germline HRR mutations found in this multinational Latin American population was lower than expected compared to previously reported rates ranging from 8% to 12% from other countries. Additionally, the most frequently mutated HRR genes differed from those from major trials including PROfound (NCT02987543). Clinical trial information: NCT04962880 . [Table: see text]

Low Prevalence of ETV6::RUNX1 Fusion Gene in a Hispanic Population

ETV6::RUNX1 is a genetic rearrangement of good prognosis in children with acute lymphoblastic leukemia (ALL). In Mexico, its prevalence is low in comparison with Caucasian populations. We developed a novel TaqMan one-step RT-qPCR approach to assess the prevalence of four genetic rearrangements in a cohort of Hispanic children with ALL from Mexico City. The prevalence of common fusion gene transcripts was as follows: TCF3::PBX1 7.7%; BCR::ABL1p 190 3.3%; and KMT2A::AFF1 2.8%, and ETV6::RUNX1was observed with low prevalence (10.5%) in comparison to that reported for developed countries. This is consistent with previous findings on Mexican children with ALL and similar to those reported on children from Hispanic populations. The confirmation of a low prevalence of ETV6::RUNX1 in children of a Hispanic origin represents an advancement in the description of genetic factors of ALL in these populations.

Mutational Landscape of CEBPA in Mexican Pediatric Acute Myeloid Leukemia Patients: Prognostic Implications

BACKGROUND

In Mexico, the incidence of acute myeloid leukemia (AML) has increased in the last few years. Mortality is higher than in developed countries, even though the same chemotherapy protocols are used. CCAAT Enhancer Binding Protein Alpha (CEBPA) mutations are recurrent in AML, influence prognosis, and help to define treatment strategies. CEBPA mutational profiles and their clinical implications have not been evaluated in Mexican pediatric AML patients.

AIM OF THE STUDY

To identify the mutational landscape of the CEBPA gene in pediatric patients with de novo AML and assess its influence on clinical features and overall survival (OS).

MATERIALS AND METHODS

DNA was extracted from bone marrow aspirates at diagnosis. Targeted massive parallel sequencing of CEBPA was performed in 80 patients.

RESULTS

CEBPA was mutated in 12.5% (10/80) of patients. Frameshifts at the N-terminal region were the most common mutations 57.14% (8/14). CEBPA biallelic (CEBPA ^BI) mutations were identified in five patients. M2 subtype was the most common in CEBPA positive patients (CEBPA ^POS) (p = 0.009); 50% of the CEBPA ^POS patients had a WBC count > 100,000 at diagnosis (p = 0.004). OS > 1 year was significantly better in CEBPA negative (CEBPA ^NEG) patients (p = 0.0001). CEBPA ^POS patients (either bi- or monoallelic) had a significantly lower OS (p = 0.002). Concurrent mutations in FLT3, CSF3R, and WT1 genes were found in CEBPA ^POS individuals. Their contribution to poor OS cannot be ruled out.

CONCLUSION

CEBPA mutational profiles in Mexican pediatric AML patients and their clinical implications were evaluated for the first time. The frequency of CEBPA ^POS was in the range reported for pediatric AML (4.5-15%). CEBPA mutations showed a negative impact on OS as opposed to the results of other studies.

Profiling FLT3 Mutations in Mexican Acute Myeloid Leukemia Pediatric Patients: Impact on Overall Survival

Background: Acute myeloid leukemia (AML) is the second most frequent leukemia in childhood. The FLT3 gene participates in hematopoietic stem cell proliferation. FLT3 mutations are recurrent in AML and influence prognosis. In Mexican pediatric AML patients, FLT3 mutational profile, and their clinical impact have not been evaluated. Aim of the study: This study aimed to identify the profile of FLT3 mutations in pediatric patients with de novo AML and to assess their possible influence on overall survival (OS) and other clinical features. Methods: Massive parallel target sequencing of FLT3 was performed in 80 patients. Results: FLT3 mutations [internal tandem duplication (ITD) or tyrosine kinase domain (TKD)] were identified in 24% of them. OS was significantly lower in FLT3 POS cases than in FLT3 NEG (p = 0.03). The average OS for FLT3 POS was 1.2 vs. 2.2 years in FLT3 NEG. There were no significant differences in the children's sex, age, percentage of blasts in bone marrow aspirate, or white blood cell count in peripheral blood at diagnosis between both groups. No differences were identified stratifying by the mutational load (high > 0.4) or type of mutation. The negative effect of FLT3 mutations was also observed in patients with acute promyelocytic leukemia (APL). Conclusions: FLT3 mutational profile is described in Mexican pediatric AML patients for the first time. Mutated FLT3 negatively impacts the outcome of AML patients, even considering the APL group. The clinical benefit from treatment with tyrosine kinase inhibitors in the FLT3 POS pediatric patients needs to be assessed in clinical trials. FLT3 testing may contribute to better risk stratification in our pediatric AML patients.